Paradoxical breathing (abdominal paradox): Mechanism

During a Respiratory exam, the question of paradoxical breathing commonly comes up. The more accurate and correct term is actually abdominal paradox (as paradoxical breathing may also refer to the deranged breathing seen during an injury resulting in flail chest).

During a normal respiratory cycle, in the supine position, the anterior abdominal wall displays a prominent outward movement during inspiration. This is secondary to diaphragm movement and displacement of abdominal viscera. The opposite is seen during expiration.

However, during abdominal paradox, as the diaphragm fatigues, it is unable to contract and move downwards. Instead of the expected outward movement of the abdominal wall, there is an inward movement instead (hence the term paradox).

MECHANISM: The paradoxical inward movement of the abdominal wall during inhalation is due to the cephalic (upward) movement of the fatiguing diaphragm in response to the negative intra-thoracic pressure generated by the inspiratory action of the neck and intercostal muscles.

EXAMPLE: Video

 REFERENCES

1. Chapter 9. Pulmonary Evaluation. Lawrence P. Cahalin. Cardiovascular and Pulmonary Physical Therapy: An Evidence-Based Approach.
2. Civetta, Taylor, & Kirby’s: Critical Care, 4th Edition Section II – Monitoring Chapter 20 – Bedside Assessment and Monitoring of Pulmonary Function and Power of Breathing in the Critically.
3. Chapter 143: Pump Failure: The Pathogenesis of Hypercapnic Respiratory Failure in Patients with Lung and Chest Wall Disease. Steven G. Kelsen. Fishman’s Pulmonary Diseases and Disorders, 5e.